System and method for detecting imbalance in a washing machine

ABSTRACT

Systems and methods for detecting imbalance in a washing machine are disclosed. The washing machine includes a wash basket that is rotatably mounted in a wash tub. The wash basket is rotated in the wash tub during a cleansing cycle or during a spin cycle to extract water from a wash load loaded in the wash basket. The system and methods of the present disclosure include a plurality of activators mounted to the wash basket and the sensor mounted to the wash tub. The sensor can generate an activation signal each time an activator passes in front of the sensor. The activation signals can be analyzed to determine imbalance in the washing machine.

FIELD OF THE INVENTION

The present disclosure relates generally to washing machines, and more particularly to a system and method for detecting imbalance in washing machines.

BACKGROUND OF THE INVENTION

Washing machines typically include a cabinet which receives a stationary tub for containing wash and rinse water. A wash basket is rotatably mounted within the wash tub. A drive assembly and a brake assembly can be positioned with respect to the wash tub and configured to rotate and control the rotation of the wash basket within the wash tub to cleanse the wash load loaded into the wash basket. During a wash cycle, water is typically extracted from the wash load by revolving the wash basket containing the wash load at a high rotational velocity. Centrifugal forces pull the majority of the water out of the wash load and through perforations in the rotating basket. A pump assembly can be used to rinse and drain the extracted water to a draining system.

The rotating basket is typically supported by a suspension system designed to dampen translational motion induced by any imbalance with in the rotating basket. High stresses are sometimes encountered within the basket, drive system, and suspension system during the high-speed spin action used for water extraction during normal wash cycles. With an imbalance within the wash load, a force is generated which is proportional to the product of the mass, the distance between the imbalance and the center of rotation, and the square of the velocity. Small imbalances can very easily generate large forces as a result of the high rotational velocities.

Known washing machines may employ various sensing techniques to determine if the machine is operating with an imbalanced load. These sensing techniques typically involve current or load sensing in the motor control. If an imbalanced load is detected during an extraction spin cycle, the machine is stopped and a signal is generated to alert the user to the imbalanced load. Other machines are configured to measure the imbalance and then decide if the imbalance is too large or if it is desirable to increase speed. Sensing techniques involving current or load sensing in the motor control can be inaccurate due to additional loads on the motor other than the load provided by any imbalance.

Thus, a need exists for an improved system and method for sensing imbalance in a washing machine that does not depend on current or load sensing in the motor control. A system and method for detecting imbalance that provides for improved spin control would be particularly useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

On exemplary embodiment of the present disclosure is directed to a washing machine. The washing machine includes a wash tub and a wash basket rotatably mounted in said wash tub. The wash basket has an outer surface facing an inner surface of the wash tub. The washing machine includes a sensor disposed on the inner surface of wash tub and a plurality of activators mounted on the outer surface of the wash basket.

Another exemplary embodiment of the present disclosure is directed to a system for monitoring imbalance in a washing machine. The washing machine includes a wash tub and a wash basket rotatably mounted in the wash tub. The wash basket has an outer surface facing an inner surface of the wash tub. The system includes a sensor mounted to the inner surface of the wash tub, a plurality of activators mounted in evenly spaced apart relationship on the outer surface of the wash basket, and a controller coupled to the sensor. The sensor provides an activation signal to the controller each time one of the plurality of activators passes in front of the sensor as the wash basket rotates in the wash tub.

A further exemplary embodiment of the present disclosure is directed to a method of determining imbalance of a wash basket as it rotates in a wash tub of a washing machine. The method includes controlling the wash basket to rotate in the wash tub such that a plurality of activators mounted in evenly spaced apart relationship on the wash basket passes in front of a sensor mounted on the wash tub; receiving an activation signal from the sensor mounted on the wash tub each time one of the plurality activators passes in front of the sensor; and determining imbalance of the wash basket based at least in part on the activation signals.

Variations and modifications can be made to these exemplary embodiments of the present disclosure.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1—provides a perspective view of a washing machine according to an exemplary embodiment of the present disclosure;

FIG. 2—provides a side elevation schematic view of the washing machine of FIG. 1—;

FIG. 3—provides of an exemplary arrangement of a sensor and a plurality of activators in a system for monitoring imbalance in washing machine according to an exemplary embodiment of the present disclosure;

FIG. 4—provides a block diagram of an exemplary control system according to an exemplary embodiment of the present disclosure;

FIG. 5—provides a graphical representation of a speed curve for an imbalanced wash basket in a washing machine according to an exemplary embodiment of the present disclosure; and

FIG. 6—provides a flow diagram of exemplary method steps according to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

In general the present disclosure is directed to a system and method for detecting imbalance in a washing machine. The washing machine includes a wash basket that is rotatably mounted in a wash tub. The wash basket is rotated in the wash tub, for example, during a cleansing cycle or during a spin cycle to extract water from a wash load loaded in the wash basket. The system and methods of the present disclosure use a plurality of activators mounted to a wash basket to determine the speed of a certain portion of the wash basket during rotation of the wash basket in the wash tub. The measurement of the speed can be correlated to an out of balance condition for the washing machine.

More particularly, a sensor can be placed in a stationary location on the back of the wash tub. A plurality of activators can be evenly spaced on the back of the rotating wash basket such that each of the plurality of activators passes in front of the sensor. The sensor can provide an activation signal to, for instance, a controller, each time an activator passes in front of the sensor. The time between activation signals is monitored and analyzed to determine imbalance in the washing machine. For instance, in a balanced condition, the time interval between activation signals is about the same. In an imbalanced condition, the time interval between activation signals is not the same. The degree of error in the time intervals between activation signals can be correlated to the degree of imbalance. The correlation can be derived through a transfer function involving speed and inertia. In particular embodiments, the controller can control rotation of the wash basket in the wash tub based at least in part on the degree of imbalance in the washing machine. In this manner, the embodiments of the present disclosure provide for improved imbalance monitoring and improved wash basket spin control.

FIG. 1—provides a perspective view of an exemplary washing machine 50 according to an exemplary embodiment of the present disclosure. Washing machine 50 includes a cabinet 52 having a front panel 54, a top panel 56, and side panels 58. A door 55 is mounted to front panel 54 and is rotatable about a hinge (not shown) between an open position (not shown) facilitating access to a basket (not shown) in the interior of washing machine 50 that holds a wash load, and a closed position (as shown in FIG. 1—) forming a substantially sealed enclosure over the basket. A control panel 60 including a plurality of input selectors 62 is coupled to an upper portion of front panel 54. Control panel 60 and input selectors 62 collectively form a user interface for operator selection of machine cycles and features, and, in one embodiment, a display section 61 indicates selected features, machine status, and other items of interest to users.

As illustrated in FIG. 1—, washing machine 50 is a horizontal axis machine. It is contemplated that the present disclosure is applicable, not only to horizontal axis machines, such as washing machine 50, but to other forms of clothes treatment machines, such as vertical axis machines. It is also contemplated that the benefits of the present disclosure accrue to other forms of clothes treatment machines, such as for example, washing/dry cleaning machines, dry cleaning machines, and washer/dryer combination machines. Therefore, washing machine 50 is provided by way of illustration rather than limitation. Accordingly, the following description is for illustrative purposes only, and there is no intention to limit application of the present invention to any clothes treatment machine, such as horizontal axis washing machine 50.

FIG. 2 is a side elevational schematic view of washing machine 50 including wash basket 70 movably disposed and rotatably mounted in wash tub 64 in a spaced apart relationship from the tub side walls. Basket 70 includes a plurality of perforations therein to facilitate fluid communication between an interior of basket 70 and wash tub 64.

A hot liquid valve 102 and a cold liquid valve 104 deliver wash fluid, such as water, to basket 70 and wash tub 64 through a respective hot liquid hose 106 and a cold liquid hose 108. Liquid valves 102, 104 and liquid hoses 106, 108 together form a liquid supply connection for washing machine 50 and, when connected to a building plumbing system (not shown), provide a fresh water supply for use in washing machine 50. Liquid valves 102, 104 and liquid hoses 106, 108 are connected to a basket inlet tube 110, and fluid is dispersed from inlet tube 110 into tub 64.

Basket 70 is driven by motor 120 through a transmission and clutch system 122. A transmission belt 124 is coupled to respective pulleys of a motor output shaft 126 and a transmission input shaft 128. Thus, as motor output shaft 126 is rotated, transmission input shaft 128 is also rotated. Clutch system 122 facilitates driving engagement of basket 70 for rotatable movement within wash tub 64, and clutch system 122 facilitates relative rotation of basket 70 for selected portions of wash cycles. Motor 120, the transmission and clutch system 122 and belt 124 collectively are referred herein as a machine drive system.

Washing machine 50 also includes a brake assembly (not shown) selectively applied or released for respectively maintaining basket 70 in a stationary position within tub 64 or for allowing basket 70 to spin within tub 64. Pump assembly 72 is selectively activated, in the example embodiment, to remove liquid from basket 70 and tub 64 through drain outlet 90 and a drain valve 130 during appropriate points in washing cycles as machine 50 is used.

Operation of machine 50 is controlled by a controller 138 which is operatively coupled to the user interface input located on washing machine control panel 60 (shown in FIG. 1—) for user manipulation to select washing machine cycles and features. In response to user manipulation of the user interface input, controller 138 operates the various components of machine 50 to execute selected machine cycles and features.

Tub 64 is suspended in the washing machine cabinet 52 by spring assemblies 140 (only one spring assembly 140 is illustrated in FIG. 2—) and damped from below using pneumatic damping devices 150. Damping devices 150 are used to damp and provide stability to tub 64 during operation.

As discussed above, wash basket 70 rotates in wash tub 64 during various portions of a wash cycle. For instance, wash basket 70 rotates at high rotational speeds within wash tub 64 during a final spin cycle to extract wash fluid from a wash load loaded in wash basket 70.

Under certain circumstances, wash basket 70 can experience imbalance due to large wash loads loaded into wash basket 70 and other factors. FIG. 5—depicts a graphical representation of an exemplary rotational speed curve for an imbalanced wash basket for a horizontal axis washing machine. As discussed above, the wash basket 70 (shown in FIG. 2—) rotates in wash tub 64 (shown in FIG. 2—) such that during a revolution, a portion of the wash basket 70 continuously rotates from a top portion of wash tub 64 to a bottom portion of wash tub 64 and returns to a top portion of wash tub 64. If wash basket 70 contains a large or imbalanced wash load, the wash basket 70 will have to overcome varying gravitational forces acting on the wash load during rotation of the wash basket 70 in the wash tub 64. The varying gravitational forces acting on the wash load can cause an out of balanced condition for the wash basket 64 as it rotates in wash tub 64.

In particular, as illustrated in FIG. 5—, the rotational speed of the wash basket 70 initially increases to peak value S2. The rotational speed of the wash basket 70 increases due to a large wash load being located at or near the top of the wash tub 64. Gravitational forces acting on the wash load will pull the wash load toward the bottom of wash tub 64, increasing the rotational speed of wash basket 70. After reaching a peak value S2, the speed of rotation of the wash basket begins to decrease to a minimum value S1. The rotational speed is reduced as a result of the wash basket 70 having to overcome gravitational forces to return the wash load to the top of the wash tub 64. In this manner, an imbalanced wash basket will have rotational speeds that fluctuate between a peak value, such as S2, and a minimum value, such as S1, during rotation of the wash basket 70 in the wash tub 64. If the imbalance of wash basket is allowed to surpass a certain threshold, the wash basket 70 and various other components of washing machine 50 could be damaged.

Referring back to FIG. 2—, washing machine 50 includes a system for monitoring imbalance of wash basket 70 as it rotates in wash tub 64. In particular, a sensor 220 is located at a stationary position on the inner surface of wash tub 64. A plurality of activators 210 are disposed on the outer surface of wash basket 70. As wash basket 70 rotates in wash tub 64, activators 210 will pass in front of sensor 220. Sensor 220 generates an activation signal every time an activator 210 passes in front of sensor 220. The activation signals generated by sensor 210 can be analyzed to determine imbalance in the wash basket 70 as it rotates in wash tub 64.

More particularly, FIG. 3—illustrates a close up view of an exemplary arrangement of sensor 220 and activators 210 on a wash basket 70 and wash tub 64 according to an exemplary embodiment of the present disclosure. Sensor 220 is disposed at a stationary location on a back inner surface 65 of wash tub 64. In FIG. 3—, back inner surface 65 has been broken away from the remainder of wash tub 64 to reveal wash basket 70 disposed in the interior of wash tub 64. As shown, a plurality of activators 210 are disposed in evenly spaced apart relationship at different azimuthal positions on the outer surface of wash basket 70. As basket 70 rotates in wash tub 64, activators 210 pass in front of sensor 220. Sensor 220 generates an activation signal every time an activator 210 passes in front of sensor 220. The imbalance of wash basket 70 can be monitored by analyzing the time intervals between successive activation signals.

In a particular embodiment, the sensor 220 comprises a Hall effect sensor and the plurality of activators 210 each comprise a magnetic material. The Hall effect sensor 220 can produce an output signal that varies in response to changes in magnetic field. As the plurality of activators 210 of magnetic material pass in front of the Hall effect sensor 220, the output signal of the Hall effect sensor 220 will exhibit a sudden change as a result of the passing magnetic activator 210. The sudden change in the output signal acts as an activation signal, indicating that an activator 210 has passed in front of sensor 220.

Those of ordinary skill in the art, using the disclosures provided herein, should understand that various other types of sensors can be used as sensor 220. For instance, in other embodiments, sensor 220 can include an optical sensor, thermal sensor, inductance sensor, capacitive sensor, or any other suitable sensor that can detect a change in various properties caused as a result of an activator 210 passing in front of sensor 220.

The output signals of sensor 220 can be provided to a controller or other processing device for analysis. The controller or other processing device can monitor the output signals of sensor 220 to determine the degree of imbalance of the wash basket 70 as it rotates in wash tub 64. The controller can be a stand alone controller or processing device or can be controller 138 (shown in FIG. 2—) used to control operation of the washing machine 50 (shown in FIG. 2—).

FIG. 4—is a schematic block diagram of an exemplary washing machine control system 160 for use with washing machine 50 (shown in FIG. 1 and FIG. 2). Control system 160 includes controller 138 which may, for example, be a microcomputer 164 coupled to a user interface input 161. An operator may enter instructions or select desired washing machine cycles and features via user interface input 161, such as through input selectors 62 (shown in FIG. 1—) and a display or indicator 61 coupled to microcomputer 164 displays appropriate messages and/or indicators, such as a timer, and other known items of interest to washing machine users. A memory 162 is also coupled to microcomputer 164 and stores instructions, calibration constants, and other information as required to satisfactorily complete a selected wash cycle. Memory 162 may, for example, be a random access memory (RAM). In alternative embodiments, other forms of memory could be used in conjunction with RAM memory, including but not limited to flash memory (FLASH), programmable read only memory (PROM), and electronically erasable programmable read only memory (EEPROM).

Power to control system 160 is supplied to controller 138 by a power supply 166 configured to be coupled to a power line L. Analog to digital and digital to analog converters (not shown) are coupled to controller 138 to implement controller inputs and executable instructions to generate controller output to washing machine components. More specifically, controller 138 is operatively coupled to machine drive system 168 (e.g., motor 120 and clutch system 122 shown in FIG. 2—), a brake system 171 associated with basket 70, machine water valves 172, including a wash fluid dispenser, and machine drain system 174 (e.g., drain pump assembly 72 and/or drain valve 130 shown in FIG. 2—) according to known methods.

In response to manipulation of user interface input 161, controller 138 monitors various operational factors of washing machine 50 with one or more sensors or transducers 176, and controller 138 executes operator selected functions and features according to known methods. Of course, controller 138 may be used to control washing machine system elements and to execute functions beyond those specifically described herein. Controller 138 can be configured operates the various components of washing machine 50 in a designated wash cycle familiar to those in the art of washing machines.

In accordance with aspects of the present disclosure, controller 138 can receive signals from imbalance monitoring sensor 220 (shown in FIGS. 2—and 3—). Controller 138 can analyze the signals received from imbalance monitoring sensor 220 to determine imbalance of the wash basket 70 (shown in FIGS. 2—and 3—) as it rotates within wash tub 70. Controller 138 can also control rotation of the wash basket 70 within the wash tub 64 (shown in FIGS. 2—and 3—) based at least in part on signals received from imbalance monitoring sensor 220. For instance, in a particular embodiment, controller 138 can stop rotation of wash basket 70 within wash tub 64 if the imbalance of wash basket 70 exceeds a threshold value. The controller 138 can provide an indication to a user that the wash basket 70 is imbalanced and the wash load need to be altered. Alternatively, the controller 138 can control the speed and direction of rotation of wash basket 70 to alter the distribution of the wash load within wash basket 70. In this manner, controller 138 can improve the rotation of wash basket 70 within wash tub 64 based on signals received from imbalance monitoring sensor 220.

FIG. 6—illustrates a flow chart of exemplary method steps of a method 600 according to an exemplary embodiment of the present disclosure. At 610, a wash basket of a washing machine is controlled to rotate in a wash tub. The wash basket has a plurality of activators evenly spaced on an outer surface of the wash basket. As the wash basket rotates, the plurality of activators pass in front of a stationary imbalance sensor mounted on an inner surface of the wash tub. The imbalance sensor generates an activation signal each time one of the plurality of activators passes in front of the imbalance sensor.

At 620, a controller or other processing device receives the activation signals from the imbalance sensor. The controller or other processing device can determine the imbalance of the wash basket based at least in part on the activation signals received from the imbalance sensor. The controller or other processing device can also control rotation of the wash basket within the wash tub based at least in part on the activation signals.

At 630, the controller or other processing device determines the time interval between activation signals. The controller or other processing device can determine imbalance of the wash basket based on the time intervals. For instance, at 640 the controller or other processing device determines the degree of error of the time interval between activation signals. The degree of error refers to the difference in time of successive time intervals between the activation signals.

At 650, the controller or other processing device determines imbalance based on the degree of error in the time intervals between the activation signals. If the degree of error is low or close to zero, the time intervals between activation signals are substantially equal. This indicates that there is little to no imbalance in the rotation of the wash basket. If the degree of error in the time intervals between activation signals is high, there is a high degree of imbalance in the rotation of the wash basket.

At 660, the controller or other processing device controls the rotation of the wash basket in the wash tub based on the degree of imbalance of the wash basket. For instance, if the degree of error in the time intervals between activation signals exceeds a threshold value, the controller or other processing device can control the wash basket to stop rotation in the wash tub. Alternatively, the controller or other processing device can control the speed and direction of rotation of the wash basket to alter the distribution of a wash load in the wash basket. In this manner, the method 600 of the present disclosure provides for improved spin control taking into account any imbalance in the wash basket as it rotates in the wash tub.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

1. A washing machine, comprising: a stationary wash tub; a wash basket rotatably mounted in said wash tub, said wash basket having an outer surface facing an inner surface of said wash tub; a sensor disposed on said inner surface of said wash tub; and a plurality of activators mounted on the outer surface of said wash basket.
 2. The washing machine of claim 1, wherein said plurality of activators are mounted in evenly spaced apart relationship on the outer surface of said wash basket.
 3. The washing machine of claim 1, wherein each of said plurality of activators is disposed on the outer surface of said wash basket such that each of said plurality of activators passes in front of said sensor during a revolution of said wash basket within said wash tub.
 4. The washing machine of claim 3, wherein said sensor is configured to provide an activation signal each time one of said plurality activators passes in front of said sensor.
 5. The washing machine of claim 3, wherein said sensor is coupled to a controller, said sensor providing an activation signal to said controller each time one of said plurality of activators passes in front of said sensor, said controller configured to determine imbalance of said wash basket based at least in part on said activation signals.
 6. The washing machine of claim 5, wherein said controller is configured to control the rotation of said wash basket in said wash tub based at least in part on the activation signals received from said sensor.
 7. The washing machine of claim 5, wherein said controller is configured to monitor the time interval between each activation signal, said controller configured to determine imbalance in the washing machine based at least in part on the time intervals between the activation signals.
 8. The washing machine of claim 1, wherein said sensor comprises a Hall sensor.
 9. The washing machine of claim 8, wherein said plurality of activators are comprised of a magnetic material.
 10. A system for monitoring imbalance in a washing machine, the washing machine comprising a wash tub and a wash basket rotatably mounted in the wash tub, the wash basket having an outer surface facing an inner surface of the wash tub, the system comprising: a sensor mounted to the inner surface of the wash tub; a plurality of activators mounted in evenly spaced apart relationship on the outer surface of the wash basket; and a controller coupled to said sensor; wherein said sensor provides an activation signal to said controller each time one of said plurality of activators passes in front of said sensor as the wash basket rotates in the wash tub.
 11. The system of claim 10, wherein said controller is configured to control rotation of the wash basket in the wash tub based at least in part on the activation signals.
 12. The system of claim 10, wherein said controller is configured to determine imbalance of the wash basket based at least in part on the activation signals.
 13. The system of claim 12, wherein said controller is configured to determine imbalance of the wash basket based on the time intervals between activation signals received from said sensor.
 14. The system of claim 10, wherein said sensor comprises a Hall sensor.
 15. The system of claim 10, wherein said plurality of activators are comprised of a magnetic material.
 16. A method of determining imbalance of a wash basket as it rotates in a wash tub of a washing machine, the method comprising: controlling the wash basket to rotate in the wash tub such that a plurality of activators mounted in evenly spaced apart relationship on the wash basket passes in front of a sensor mounted on the wash tub; receiving an activation signal from the sensor mounted on the wash tub each time one of the plurality activators passes in front of the sensor; and determining imbalance of the wash basket based at least in part on the activation signals.
 17. The method of claim 16, wherein the method further comprises controlling the rotation of the wash basket in the wash tub based at least in part on the activation signals.
 18. The method of claim 16, wherein determining imbalance of the wash basket comprises: monitoring the time intervals between activation signals; and determining imbalance based at least in part on the time intervals between activation signals.
 19. The method of claim 18, wherein the method comprises: determining a degree of error of the time intervals between activation signals; comparing the degree of error to a threshold value; controlling the rotation of the wash basket when the degree of error exceeds the threshold value.
 20. The method of claim 18, wherein determining imbalance based at least in part on the time between activation signals comprises: determining a degree of error of the time intervals between activation signals; determining imbalance as a function of the degree of error of the time between activation signals. 